vpnor: Shuffle and rework includes for sanity

Include ordering and whether or not C linkage is forced by `extern "C"`
blocks can cause headaches at link time. Ensure that all C dependencies
are included in an `extern C` block before other includes occur. Also
include the C++ versions of string.h and assert.h

Change-Id: Ia96f6044d40c8eccb907b65924efcf62ac7a89c3
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/vpnor/test/dump_flash.cpp b/vpnor/test/dump_flash.cpp
index 84a88d8..5179b7c 100644
--- a/vpnor/test/dump_flash.cpp
+++ b/vpnor/test/dump_flash.cpp
@@ -3,19 +3,19 @@
 
 #include "config.h"
 
-#include <assert.h>
-#include <string.h>
-
-#include "transport_mbox.h"
-#include "vpnor/mboxd_pnor_partition_table.h"
-
 extern "C" {
 #include "test/mbox.h"
 #include "test/system.h"
+#include "transport_mbox.h"
 }
 
 #include "vpnor/test/tmpd.hpp"
 
+#include <cassert>
+#include <cstring>
+
+#include "vpnor/mboxd_pnor_partition_table.h"
+
 struct test_context
 {
     uint8_t seq;